Primary extraskeletal osteosarcoma of sigmoid mesocolon: a case report and a review of the literature

Abstract Background Extraskeletal osteosarcoma (ESOS) is a rare mesenchymal malignancy, which produces osteoid, bone, or chondroid material and located in the soft tissue without attachment to skeletal bones periosteum. One of things that ESOS originated from mesentery much rarer. Case presentation A 75-year female had history pain left lower abdomen for more than 4 months. Abdominal computerized tomography (CT) magnetic resonance imaging revealed large, irregular, solid-cystic mass (largest diameter was 11.5 cm). The tumor radically removed during an open operation. It composed abundant osteoid polyhedral-shaped cells with high atypia mitotic activity microscopically. final pathological diagnosis osteoblastic osteosarcoma, arising sigmoid mesocolon negative margins. 9-month follow-up by CT exhibited signs peritoneal metastasis. Conclusions Given rarity cases mesenteric ESOS, mainly depended on pathology findings should be taken into consideration when found. Its most effective treatment not been determined, surgical excision being generally accepted. Ensuring margins may important factor affecting prognosis.